Combining HD & SD in a timeline

We need guidance to combine Standard Definition (SD) and High Definition (HD) video in a single FCP timeline. All footage was shot on a Panasonic HVX-200, the crucial difference being that the first 30 hours were shot in 16:9 24P SD on mini DV tape and the other 70 hours were shot in 720 (24P) HD on P2 cards. Can these two formats be combined in a timeline? Do we first need to up-res the SD or downscale the HD? Please advise!